未捕获的错误:在C:\ xampp \ htdocs \ Android \ DbOperations.php:15中调用null成员函数bind_param()堆栈跟踪:#0 C:\ xampp \ htdocs \ Android \ registerUser.php(19 ):DbOperations-> createUser('ayush','kackacc','erthyuklo')#1 {main}抛出在第15行的C:\ xampp \ htdocs \ Android \ DbOperations.php中